Various flat multiple conductor cables are well known in the art and are available commercially. In the past a principal obstacle to wide spread adoption of multiple conductor cables has been the relatively high manufacturing cost due primarily to direct labor costs. Another factor limiting wide spread adoption of multiple conductor cables is the inability of the art to simply and economically produce cables to custom designs.
It has been proposed in U.S. Pat. No. 4,357,750 (assigned to the assignee of the present application) to produce an electrical cable comprising a plurality of spaced metallic conductors formed from a monolithic rigid metallic sheet by selectively reducing the sheet in cross-section so as to define conductor patterns with integral terminal ends, and to render flexible, desired areas of the conductors. Two chemical milling (etching) steps are disclosed, the first of which is to remove metal from selected portions on one face of the sheet and the second of which is to remove metal from selected portions from the opposite face of the sheet until breakthrough occurs leaving a plurality of flexible conductors integral with rigid terminals.
The method of producing electrical cable proposed in U.S. Pat. No. 4,357,750 involves difficulty in controlling the depth (the Z axis) of metal removal in the chemical milling steps which in turn limits the accuracy with which the thickness and width of conductors can be produced. Typically, in such a method, there results a 25% variation in thickness which results in a 25% variation in reduction of conductor width. This is a consequence of the fact that chemical milling proceeds more or less at an angle, from the surface being etched, such that for each unit of thickness of metal thickness removed, the width of an adjacent feature is reduced. The limitations mentioned result in constraints in the width, thickness and spacing of conductors which may be produced with the consequent limitation of the application of the method of U.S. Pat. No. 4,357,750 to densely packed conductors and terminals.
Cables produced in accordance with U.S. Pat. No. 4,357,750 must be carefully designed in order to avoid fatigue problems at the transitions from relatively flexible conductors to relatively rigid terminals in situations involving repeated flexing of these transitions and this limits freedom of design and range of applications.
It is an object of the present invention to provide a novel laminate suitable for producing improved multiple conductor cables having flexible portions and rigid terminals.
Another object of the present invention is to provide a relatively simple and inexpensive method for producing a cable of the type above described with an improved conductor packing density potential.
Yet another object of the present invention is to provide a novel multiple conductor cable having relatively flexible conductors integral with relatively rigid terminals.
Yet another object of the present invention is to provide reinforcement of the transition from the relatively flexible conductors to the relatively rigid terminals to reduce fatigue problems at this transition.